Variable-capacity turbine

ABSTRACT

Exhaust gas that is supplied to a turbine, but without going through channels between nozzle vanes provided in a variable-capacity turbocharger, is eliminated. A nozzle unit  100  in turbocharger  10  has a mounting plate  102  and a side plate  106  installed in a recess  20   a  provided in a housing  20  such that the side plate can move in the recess. A pushing mechanism  116  or  150  pushes the side plate toward the mounting plate  102.  A movement limit  108  limits the movement of the side plate parallel to the turbine shaft toward the mounting plate  102.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention concerns a variable-capacity turbocharger. Morespecifically, it concerns an improvement of a nozzle unit for supplyingexhaust gases to a turbine of the turbocharger.

2. Description of the Related Art

A turbocharger is an effective means to increase the output of aninternal combustion engine. A turbine is rotated by the exhaust gas fromthe engine, and a compressor mounted on the same shaft as the turbinepressurizes the air supplied to the engine. Turbochargers are currentlyinstalled in a variety of engines. However, the flow rate of the exhaustgas varies with the speed of the engine's revolution. The flow rate ofthe exhaust gas which is actually supplied from the engine will notalways be that needed to produce the ideal operating conditions for thesupercharger. To rectify this situation and allow the turbocharger'scapacity to be used to its best advantage, a variable-capacityturbocharger has been developed. In a variable-capacity turbocharger,the flow of the exhaust gas in the turbine compartment is regulatedaccording to the operating state of the internal combustion engine.

This sort of variable-capacity turbocharger has a number of nozzle vaneson the nozzle unit of the turbine, which is inside a housing. FIG. 8shows a partial cross section of the nozzle unit in a variable-capacityturbocharger belonging to the prior art.

In FIG. 8, turbine 228 is supported by bearings in a main housing of thevariable-capacity turbocharger in such a way that it is free to rotate.The exhaust gas from the internal combustion engine flows into housing220 through an intake port of the variable-capacity turbocharger. It issupplied to turbine 228 by way of scroll channel 226 which is formed inhousing 220 and nozzle unit 210 which forms the inlet to the turbine228. The exhaust gas supplied to turbine 228 is then exhausted throughthe exhaust port after it has driven the turbine 228.

Nozzle unit 210 comprises mounting plate 202, which is fixed to housing220, and side plate 206, which is placed opposite mounting plate 202. Anumber of nozzle vanes 204 are placed at equal intervals along thecircumference between the two plates. Side plate 206 is fixed tomounting plate 202 by supporting bolt 208, which goes through the plate206. Nozzle vanes 204 have a shaft portion. They are mounted on mountingplate 202 in such a way that they are free to rotate with the shaftportion.

Because side plate 206 is fixed in place by support bolt 208, the heatof the exhaust gas which is supplied to the turbine raises itstemperature, causing it to thermally deform. A space is provided betweennozzle vanes 204 and side plate 206, as in FIG. 8, in order to preventnozzle vanes 204 from catching or sticking during rotation and allowthem to operate smoothly. This is why in variable-capacity turbochargersof the prior art a portion of the exhaust gas being supplied to scrollchannel 226 is routed through the space between nozzle vanes 204 andside plate 206 and supplied to turbine 228 without going through thearea around nozzle vanes 204. In the prior art design, then, becausesome of the gas is supplied to turbine 228 without passing through thechannel around vanes 204, the efficiency of the variable-capacityturbocharger decreases.

SUMMARY OF THE INVENTION

This invention is to solve the shortcomings of the prior art designdescribed above. The object of this invention is to minimize as much aspossible or eliminate the quantity of exhaust gas supplied to theturbine without going through the channels between the nozzle vanes.This invention is also effective at minimizing the quantity of exhaustgas supplied to the turbine from behind the side plate without goingthrough the nozzle unit.

A variable-capacity turbocharger which controls the opening degree ofnozzle vanes has a turbine provided in a housing, which is free torotate on a turbine shaft, a plurality of nozzle vanes arranged innozzle units around the turbine in the housing, a link plate whichrotates freely around the turbine provided in the housing, which isconnected to the nozzle vanes by means of a plurality of levers, andwhich continuously moves the nozzle vanes synchronously between the openand closed positions, and an actuator outside the housing, which isconnected to the link plate through a transmission mechanism. Theturbocharger according to this invention is distinguished by thefollowing features. It has a mounting plate fixed to the housing, and aside plate installed in a recess provided in the housing in such a waythat the side plate can move in the recess, both of which are providedparallel to the turbine shaft. A pushing means pushes the side platetoward the mounting plate and a limiting means limits the movement ofthe side plate parallel to the turbine shaft toward the mounting plate.

The pushing means to push the side plate can be a pressure chambercreated between the side plate and the recess, or a spring plate mountedbetween the side plate and the recess.

The side plate has a doughnut shape whose center is the turbine shaft.The recess has a diameter slightly greater than the diameter of the sideplate, and the recess also has, on the inner surface, a round projectionwhich protrudes parallel to the turbine shaft toward the side plate. Thespring plate is engaged with and fixed to the round projection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a lateral view of the exterior of a variable-capacityturbocharger in which this invention is implemented.

FIG. 2 is a cross section of a turbine compartment in the firstpreferred embodiment.

FIG. 3 is a partially cut away frontal view of the variable-capacityturbocharger in FIG. 1.

FIG. 4 is an enlargement of a portion of FIG. 3. It shows a transmissionmechanism which transmits the action of an actuator to a link plate andthe elements which link the two.

FIG. 5 is a plan view of the link plate.

FIG. 6 is an exploded view of the transmission mechanism to transmit theaction of the actuator to the link plate.

FIG. 7 is a cross section of the turbine compartment in the secondpreferred embodiment of this invention.

FIG. 8 is a partial enlarged cross section of a nozzle unit belonging tothe prior art.

In these drawings, 10 is a turbine casing, 50 is an actuator, 52 is arod, 54 is a link member, 104 is a nozzle vane, 106 is a side plate, 112is a link plate, 116 is a spring plate, 114 is a lever, 120 is aswinging member, 130 is a bridge, 140 is a roller, and 150 is a pressurechamber.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In this section we shall explain several preferred embodiments of thisinvention with reference to the appended drawings. The scope of theinvention is not limited only to the parts shown, along with the shapes,relative positions and other aspects of the parts described in theembodiments, which are meant merely for the purpose of illustration.

In this section we shall explain two preferred embodiments of theinvention with reference to the appended drawings.

FIG. 1 illustrates the external appearance of a variable-capacityturbocharger 10 in which this invention has been implemented.Variable-capacity turbocharger 10 includes a housing, which comprisesturbine housing 20, compressor housing 40 and main housing 30, which isbetween turbine housing 20 and compressor housing 40. Turbine housing 20has an intake port 22 and an exhaust port 24. Compressor housing 40 hasan intake port 44 and a discharge port 42.

On the outside of the housings 20, 30 and 40 is an actuator 50, whichdrives the nozzle vanes (to be explained shortly). Actuator 50 uses airpressure, or more specifically it uses the negative pressure of the airsucked into the internal combustion engine (not pictured) on which thevariable-capacity turbocharger 10 is installed, to cause rod 52 to moveforward and back.

The turbine compartment, especially main housing, according to the firstpreferred embodiment is shown in FIG. 2. As can be seen in FIG. 2,turbine shaft 32 is supported in main housing 30 in such a way that itis free to rotate. Turbine 28, which is mounted to one end of turbineshaft 32, is inside turbine housing 20. The compressor impeller (notpictured), of course, is mounted to the other end of turbine shaft 32 incompressor housing 40. The exhaust gas from the internal combustionengine is conducted from intake port 22 into turbine housing 20. It issupplied to turbine 28 through scroll channel 26, which is created onthe inside of turbine housing 20, and nozzle unit 100, which is theinlet to turbine 28. After it drives the turbine 28, the exhaust gaswhich was supplied is exhausted through exhaust port 24.

Nozzle unit 100 comprises mounting plate 102, which is fixed to turbinehousing 20, and side plate 106, which faces mounting plate 102 and ismounted in the axial direction. A number of nozzle vanes 104 are placedbetween the two plates at regular intervals along the circumference ofthe shaft. Side plate 106 is a circular component which extends in aradial direction in a plane perpendicular to the axis of the shaft ofturbine 28. It is mounted in such a way that it can move in the axialdirection in recess 20 a, a recess provided for it in turbine housing20. In nozzle unit 100, a number of support bolts 108 are provided atregular intervals along the circumference of the shaft to serve as astop or means to limit the movement of side plate 106 in the axialdirection toward mounting plate 102.

As mentioned, in prior art designs a space is provided between sideplate 106 and nozzle vanes 104 to accommodate the thermal deformation ofside plate 106. With this embodiment, as shall be explained shortly, thedifference in the dimensions of the outer diameter of side plate 106 andthe inner diameter of recess 20 a is the minimal difference which willstill allow side plate 106 to move in the axial direction. The spacebetween side plate 106 and nozzle vanes 104 thus effectively becomesnonexistent.

A spring plate 116 is provided between side plate 106 and turbinehousing 20 as a pushing means to push the side plate. Spring plate 116has an annular portion 116 a, which is on a surface roughlyperpendicular to the axis of turbine 28, and a cylindrical mountingportion 116 b, which extends in the axial direction toward turbine 28from the inner edge of the flange 116 a. Annular portion 116 a of springplate 116 is in contact with the back of side plate 106, i.e., thesurface of side plate 106 which is opposite nozzle unit 100. Mountingportion 116 b engages with annular projection 20 b which protrudes fromthe surface of recess 20 a in the axial direction toward side plate 106.

At the base of nozzle vanes 104 is shaft portion 104 a, which is mountedto mounting plate 102 so that portion 104 a is free to rotate the vanesbetween the open and closed positions. As shown in FIGS. 3 and 4, an end104 b of each shaft portion 104 a of nozzle vane assembly 104 goesthrough mounting plate 102 in the axial direction. The shafts areconnected to various levers 114 which correspond to the nozzle vanes.(See FIGS. 3 and 4). The nozzle vane 104 rotates via nozzle shaft 104 aaccording to the rotation of lever 114. Each lever 114 has a hole 114 bto receive the end 104 b of one of the shaft portions 104 a and a bossor shaft portion 114 a on the side opposite the hole 114 b.

The shaft 114 a of lever 114 can slide within an oblong hole 112 dprovided at regular intervals along the circumference of link plate 112.As shown in FIG. 2, there is a cylindrical boss 102 a on the side ofmounting plate 102 opposite nozzle unit 100. The annular link plate 112(See FIG. 5) is mounted to the boss 102 a so that it is free to rotateon the rotational axis of turbine 28. Link plate 112 has a series ofoblong holes 112 d at regular intervals along its circumference toreceive the shaft portions 114 a of levers 114. Further, link plate 112has, on the same surface, a trapezoidal elongated portion 112 a on oneside. The end of the elongated portion 112 a is divided into twoportions to form locking arms 112 c. The two arms 112 c form arectangular recess 112 b.

The variable-capacity turbocharger 10 of this embodiment also has atransmission mechanism to transmit the action of the actuator 50 to linkplate 112 as shown in FIGS. 1 and 2. The transmission mechanism includesrod 52 of actuator 50, link member 54 (see FIG. 1), which is connectedto the end of rod 52 by pin 50 a, swinging member 120 (see FIGS. 2 and6), which is connected to the link member 54, and roller 140 and bridge130, which are between member 120 and link plate 112, and which serve toconnect the transmission mechanism to link plate 112.

As can be seen in FIG. 6, swinging member 120 comprises arm 122, shaft124, which extends along a given axis O from one end of arm 122, and issupported by turbine housing 20 through sleeve 118 in such a way that itcan freely rotate, connector 128, which is on the end of shaft 124 andcoaxial with it, and connected to link member 54 in such a way that itcannot move relative to the link member, and pin 126, which extends fromthe side of arm 122 opposite shaft 124 and is parallel to that shaft.Swinging member 120 may be made of a metallic material, for example,stainless steel. Ideally, it should be formed of a single piece ofaustenitic stainless steel. Swinging member 120, arm 122, shaft 124,connector 128 and pin 126 may be formed separately and welded together.

Bridge 130 comprises two flat plates 132, which are positioned parallelto each other with a slight gap between them, and center unit 134, whichconnects the two plates 132. At the center unit 134 provided between thetwo plates 132 is a groove 136 in which the locking arms 112 c of linkplate 112 engage. Part of bridge 130, including center unit 134, isremoved to the middle of the bridge to form cut-away portion 138. Thetwo opposed surfaces are parallel and slide against each other. As canbe seen in FIG. 6, when the transmission mechanism is assembled, thelocking unit is formed when cut-away portion 138 goes into roller 140,which is mounted on pin 126 of swinging member 120. Bridge 130 may bemade of a metallic material, for example, austenitic stainless steel.

As shown in FIG. 6, roller 140 is roughly cylindrical, with the diameterof it's opening slightly larger than the exterior diameter of pin 126.The exterior diameter of the roller is slightly smaller than the gapbetween the sliding surfaces 138 of bridge 130. Roller 140 may be madeof a metallic material, for example, martensite stainless steel.

In this section we shall explain how this embodiment operates.

When the internal combustion engine operates, as shown in FIG. 1, anegative intake pressure is created according to its rate of revolutionand the openness of its throttle, and then the pressure is controlled bya magnetic valve to transmit it to the actuator 50. The actuator 50operates according to this pressure. Rod 52 moves forward and back inthe axial direction (to the right and left in FIG. 1) according to themagnitude of the negative intake pressure. When rod 52 operates, linkmember 54 rotates on shaft 124 of swinging member 120 in response. Ascan be seen in FIG. 1, link member 54, which is shown by solid lines, isin contact with bolt 56 a on the top of stop 56. At this point nozzlevanes 104 are in the open position, the position which produces themaximum nozzle opening. When the engine is operating at low r.p.m., orthe throttle is only slightly open, actuator 50 draws back rod 52. Asrod 52 draws as far back as it can go, link member 54 moves into aposition in which it is in contact with bolt 56 b on the lower portionof stop 56, as shown by the dotted lines. At this point nozzle vanes 104are in the position which produces the smallest nozzle opening.

In this way the linear movement of rod 52 is converted by link member 54into the swinging motion of swinging member 120. Pin 126 of member 120moves in an arc around axis O of shaft 122 as shown in FIGS. 4 and 5. Atthis point pin 126 and roller 140 are in cut-away portion 138 in bridge130, and the pin is between roller 140 and a surface. It slides upwardand downward against bridge 130 in the relationship shown in FIG. 6,i.e., it slides along the axis of rotation of turbine 28. At the sametime link plate 112 rotates around the circumference of boss 102 a onmounting plate 102, with the rotary axis of turbine 28 as its center.When link plate 112 rotates, lever 114, which is connected to link plate112, rotates along with nozzle vanes 104 with shaft 104 a of vanes 104as its center.

As has been discussed, in prior art designs a space is provided betweenside plate 106 and nozzle vanes 104 to accommodate the thermaldeformation of side plate 106. For this reason prior art designs alloweda portion of the exhaust gas which should have gone into the channelbetween scroll channel 26 and nozzle vanes 104 to bypass the areabetween side plate 106 and nozzle vanes 104, i.e., the channel formed bynozzle vanes 104, and be supplied directly to turbine 28. This causesthe efficiency of variable-capacity turbocharger 10 to decrease.

In the prior art design, side plate 206 was fixed to mounting plate 202by support bolt 208. To accommodate the thermal deformation whichoccurred when the temperature of side plate 206 rose, a space had to beleft between side plate 206 and nozzle vanes 204. A portion of theexhaust gas was conducted from the channel between the exterior surfaceof the side plate and the interior surface of the recess for the sideplate along the outside or back of the side plate, i.e., along thesurface of the side plate's main housing 30. This gas was supplied tothe turbine without passing through nozzle unit 100. This too caused theefficiency of variable-capacity turbocharger 10 to decrease. It was verydifficult in the prior art to reduce the quantity of gas diverted inthis way.

With this embodiment according to this invention, side plate 106 ismounted in recess 20 a so that it can move in the axial direction. Itsposition is determined by spring plate 116, which pushes against ittoward support bolt 108. Thus even if side plate 106 should become hungup in the radial direction in recess 20 a, it will still be able to movein the axial direction. The thermal deformation of side plate 106 isabsorbed within its axial movement. This allows the space between sideplate 106 and nozzle vanes 104 to be essentially eliminated.

In the embodiment we have been discussing, instead of side plate 206being fixed to mounting plate 202 by support bolt 208 as in the previousart (see FIG. 8), the position of side plate 106 with respect tomounting plate 102 is determined by allowing it to move in the axialdirection. Thus the thermal deformation of side plate 106 is absorbedwithin its axial movement. When side plate 106 engages in recess 20 a,it is immobilized in its radial direction. Spring plate 116 pushes ittoward support bolt 108 and immobilizes it in the axial direction. Thusside plate 106 is held in position with respect to mounting plate 102.In the axial direction, the only force operating on side plate 106 inthe direction of support bolt 108 is provided by spring plate 116. Thusthe thermal deformation of side plate 106 is absorbed by its axialmovement.

The pushing means used to push side plate 106 against support bolt 108to support bolt 108 need not be limited to the spring plate 116 shown inFIG. 2. Any means may be used which pushes side plate 106 toward supportbolt 108 while allowing it to move in the axial direction.

The second preferred embodiment according to this invention is shown inFIG. 7. In this embodiment, all aspects of the configuration aside fromthe pushing means to push the side plate are identical to those of theprevious embodiment, so we shall not discuss them further, but shallexplain only those aspects which are different. Elements in FIG. 7 whichare identical to those in the previous embodiment have been given thesame reference number.

In FIG. 7, recess 20 a of turbine housing 20 contains side plate 106 andpressure chamber 150, which form the pushing means to push the sideplate. If we compare annular projection 150 a in the embodiment in FIG.7 with the annular projection 20b in the embodiment in FIG. 2, we seethat the former is substantially longer in its axial dimension so thatit comes in contact with the back of side plate 106. In the embodimentin FIG. 7, just as in the previous embodiment shown in FIG. 2, thedifference between the dimensions of the interior diameter of recess 20a and exterior diameter of side plate 106 is the smallest possibledifference which will allow side plate 106 to move in the axialdirection. However, in order to completely prevent the exhaust gas fromleaking out of the space, the pressure in the pressure chamber is madegreater than that of nozzle unit 100. As a result, side plate 106 ispushed toward support bolt 108 just as in the embodiment in FIG. 2. Tomake the pressure in chamber 150 even higher, an annular seal 152 may beprovided between annular projection 150 a and the rear surface of sideplate 106.

What is claimed is:
 1. A variable-capacity turbocharger which controlsan opening degree of nozzle vanes, comprising: a turbine provided in ahousing, said turbine being free to rotate on a turbine shaft; a nozzleunit comprising a plurality of nozzle vanes arranged around said turbinein said housing; a link plate which is provided in said housing andwhich is freely rotatable around said turbine, said link plate beingconnected to said nozzle vanes by a plurality of levers and operable tomove said nozzle vanes between open and closed positions; and anactuator which is outside of said housing and which is connected to saidlink plate through a transmission mechanism; wherein said nozzle unitfurther comprises: a mounting plate fixed to said housing and a sideplate provided in a recess in said housing such that said side plate ismovable in said recess, said nozzle vanes extending from said mountingplate toward said side plate; a spring plate pushing said side platetoward said mounting plate within said recess and absorbing thermaldeformation of said side plate, wherein said recess limits movement ofsaid side plate due to thermal deformation in a radial direction of saidturbine while allowing movement of said side plate in an axial directionof said turbine; and a support bolt arranged to limit movement of saidside plate toward said mounting plate in a direction parallel to saidturbine.
 2. A variable-capacity turbocharger which controls an openingdegree of nozzle vanes, comprising: a turbine provided in a housing,said turbine being free to rotate on a turbine shaft; a nozzle unitcomprising a plurality of nozzle vanes arranged around said turbine insaid housing; a link plate which is provided in said housing and whichis freely rotatable around said turbine, said link plate being connectedto said nozzle vanes by a plurality of levers and operable to move saidnozzle vanes between open and closed positions; an actuator which isoutside of said housing and which is connected to said link platethrough a transmission mechanism; wherein said nozzle unit comprises: amounting plate fixed to said housing and a side plate provided in arecess in said housing such that said side plate is movable in saidrecess; a pressure chamber between said side plate and said recessoperable to push said side plate toward said mounting plate; and alimiting means for limiting movement of said side plate parallel to saidturbine shaft toward said mounting plate.
 3. A variable-capacityturbocharger which controls an opening degree of nozzle vanes,comprising: a turbine provided in a housing, said turbine being free torotate on a turbine shaft; a nozzle unit comprising a plurality ofnozzle vanes arranged around said turbine in said housing; a link platewhich is provided in said housing and which is freely rotatable aroundsaid turbine, said link plate being connected to said nozzle vanes by aplurality of levers and operable to move said nozzle vanes between openand closed positions; an actuator which is outside of said housing andwhich is connected to said link plate through a transmission mechanism;wherein said nozzle unit comprises: a mounting plate fixed to saidhousing and a side plate provided in a recess in said housing such thatsaid side plate is movable in said recess; a spring plate mountedbetween said side plate and said recess operable to push said side platetoward said mounting plate; and a limiting means for limiting movementof said side plate parallel to said turbine shaft toward said mountingplate. 4.The variable-capacity turbocharger of claim 3, wherein saidside plate has a doughnut shape centered on said turbine shaft, saidrecess has a diameter slightly greater than the diameter of said sideplate, said recess has an annular projection on an inner surface thereofwhich protrudes parallel to said turbine shaft toward said side plate,and said spring plate is engaged with and fixed to said roundprojection.
 5. A variable-capacity turbocharger, comprising: a turbineprovided in a housing, said turbine being free to rotate on a turbineshaft; a nozzle unit comprising: a plurality of nozzle vanes arrangedaround said turbine, a mounting plate fixed with respect to saidhousing, said nozzle vanes being mounted on said mounting plate, a sideplate provided in a recess of said housing so as to be movable in saidrecess, and said nozzle vanes extending from said mounting plate towardsaid side plate, a pushing mechanism in said recess operable to pushsaid side plate toward said mounting plate such that space between saidside plate and said nozzle vanes is essentially eliminated, and a stopoperable to limit movement of said side plate in a direction parallel tosaid turbine shaft and toward said mounting plate; a link plate providedin said housing wherein said link plate is rotatable around saidturbine, and said link plate is connected to said nozzle vanes by aplurality of levers and operable to move said nozzle vanes between openand closed positions; and an actuator outside of said housing andconnected to said link plate through a transmission mechanism.
 6. Thevariable-capacity turbocharger of claim 5, wherein said pushingmechanism comprises a pressure chamber between said recess and said sideplate.
 7. The variable-capacity turbocharger of claim 5, wherein saidpushing mechanism comprises a spring plate mounted between said recessand said side plate.